COFFEE WASTE BIOCHAR: CHARACTERIZATION AND ZINC ADSORPTION FROM AQUEOUS SOLUTION

Lindiamara Sertoli,Cleide Aparecida De Abreu,Ruan Carnier,Leônicas Carrijo Azevedo Melo,Aline Renée Coscione

doi:10.25186/cs.v14i4.1634

Abstract

The final disposal of organic wastes has become a major challenge with increasing industrialization and population growth. Coffee wastes are examples of this, thus the conversion of these biomasses into biochar through pyrolysis could provide economic and environmental benefits, such as remediation of heavy metal polluted water. Therefore, in this work, biochar produced at 700 °C from spent coffee grounds and coffee parchment were evaluated for Zn removal from aqueous solution. Batch adsorption tests were performed with six Zn concentrations and four replicates for each material. The desorption process was performed sequentially with a pH 4.9 buffer acetic acid solution. Langmuir and Freundlich isotherms were fitted to the adsorption data using non-linear models. Batch adsorption tests showed that the adsorption was strongly dependent on biochar properties. Biochar prepared from coffee parchment was more effective at Zn binding, showing the highest adsorption capacity (0.792 mg g<sup>-1</sup>). Nevertheless, both biochars bounded Zn strongly and the adsorption process was not easily reversed.

Highlights

Heavy metals are important environmental pollutants that may originate from several anthropogenic sources and are widespread (MA et al, 2014; HOU et al, 2016; HOU and Li, 2017)
The pH values observed in both biochar samples is within the range normally found in literature for coffee wastes prepared at similar pyrolysis temperature (TANGMANKONGWORAKOON, 2019) (Table 1)
The total carbon is significantly higher than the organic carbon (OC), which can be attributed to more resilient form of C, such as aromatic C, not mineralized by the dichromate oxidation procedure

Summary

Introduction

Heavy metals are important environmental pollutants that may originate from several anthropogenic sources and are widespread (MA et al, 2014; HOU et al, 2016; HOU and Li, 2017). Mining and smelting activities generate tailings with high concentrations of heavy metals, such as zinc (Zn), lead (Pb), cadmium (Cd), copper (Cu), etc. These elements are characterized by high toxicity and long-term persistence, which can lead to harmful effects on the environment and human health, when the metal enters the trophic chain (VENEGAS et al, 2015; XU et al, 2018). Soils and sediments in mining areas present high concentrations of these elements that can transfer to plants or to water bodies. Several works demonstrated the potential of biochar to improve soil fertility characteristics (LYCHUK et al, 2015; DING et al, 2016), in the remediation of heavy metal polluted soils (PAZ-FERREIRO et al, 2017; WANG et al, 2017) and heavy metal polluted water (DOUMER et al, 2016; KONKIENE and BALTRENAITE, 2016; PATRA et al, 2017)

Objectives

Methods

Results